1. Field of the Invention
The present invention relates to a liquid ejection head and an image forming apparatus, and more particularly, to a structure of a cleaning device which wipes and cleans the ejection port surface (nozzle surface) of a liquid ejection head, and an image forming apparatus, such an inkjet recording apparatus, which adopts this structure.
2. Description of the Related Art
An inkjet recording apparatus applies ink to a recording medium, such as recording paper, by ejecting ink droplets from the nozzles of a recording head (also called a print head), and records text or images (hereinafter, referred to generally as “images”) by means of the dots of applied ink, and therefore, a portion of the ink ejected from the nozzles is dispersed in the form of a fine mist which becomes attached to the nozzle surface.
When ink mist, recording paper dust (small pieces of paper), or other types of foreign matter become attached to the vicinity of the nozzles, then it may cause the ink ejection ports (nozzle holes) to become blocked, or cause the ink ejection direction (direction of flight) to change, and hence high-quality printing cannot be achieved.
In order to prevent this, a head cleaning method is widely used, in which the nozzle surface is wiped with a wiper blade (also called simply a “wiper” or “blade”) made of a soft material, such as rubber, thereby eliminating material adhering to the vicinity of the nozzles (see Japanese Patent Application Publication Nos. 7-246708, 2-202452, 3-222754 and 2004-130595).
In respect of head cleaning technology of this kind, Japanese Patent Application Publication No. 7-246708 discloses a method for determining the state of wetting of the nozzle surface by means of optical determination, and reducing the number of cleaning operations performed, and the amount of ink consumed, by using suctioning and wiping in a selective fashion. Japanese Patent Application Publication No. 7-246708 discloses that a selection is made whether to perform suctioning or wiping, in accordance with the determination results of the state of wetting of the nozzle surface; however, there is no disclosure regarding technology for improving the cleaning performance achieved by wiping.
Japanese Patent Application Publication No. 2-202452 discloses technology which seeks to reduce wear of the liquid repelling film on a nozzle surface, as well as reducing color mixing, by disposing a cleaning device which is used conjointly with a capping device, and cleaning the nozzle groups selectively only in those heads which require cleaning. However, there is no mention of a method for increasing the cleaning efficiency of wiping.
Japanese Patent Application Publication No. 3-222754 discloses technology for detecting cases where restoration operations have been performed consecutively for a prescribed time period, and changing the free length (amount of projection) of a wiping member, thereby successively increasing the bending rigidity of the member, in such a manner that wiping efficiency is improved and the durability of the nozzle surface and the wiping member is improved. Japanese Patent Application Publication No. 3-222754 discloses technology for altering the rigidity of a wiping member by comparison with set restoration operation intervals; however, this simply changes the rigidity of the blade by inferring the state of the nozzles from the timing of the previous cleaning operation, and although it aims to increase the cleaning effect, it takes time until suitable cleaning becomes possible.
Japanese Patent Application Publication No. 2004-130595 discloses technology for an inkjet recording apparatus, provided with a counter which measures the number of wiping actions (number of wipes) and a device for previously storing a reference value for the performable number of wipes, in which the number of the counter is compared with the reference value and a report regarding replacement of the wiping member is provided to the user. Therefore, replacement of the wiping member can be prompted at a suitable time, and decline in print quality due to degraded wiping functions can be prevented in advance. However, Japanese Patent Application Publication No. 2004-130595 simply prompts replacement of the blade to the user, and does not disclose means for improving the cleaning capability.